Re: [Scilab-users] Simulating phase modulation
Hi Gary Thanks for your input. I went the analytic route for now, and simplified a bit (as you often do with analytic solutions). You're right that from an electro-mechanical point of view, superposition applies, but as the waves transmit in acoustics in air - not, I'm afraid, this is where we see the distortion, simply because the speaker cone moves several millimeter. Best regards, Claus On Sat, May 26, 2018 at 10:55 PM Gary Nelson <porpoisesee...@gmail.com> wrote: > Claus, > > Back in the late 60s, I did my PhD research using analytic signal. Yes,it > works, and the implementation details are more complex that we find on the > link. A few years ago, I implemented a system for analyzing harbor porpoise > vocalizations using scilab. For example, instantaneous phase(t) wants to be > differentiable if instantaneous frequency is to be positive. I found that > octave bands are the widest that preserves this feature. Yes, you can > calculate phase(t) = atan(imaginary/real), but you have to add 2PI when > atan wraps around in order to make phase monotonically increase. > > > > Also, I am not convinced that a loudspeaker does phase modulation. > Certainly, if the speaker is linear, then superposition applies. If phase > modulation occurs, it is a non-linear effect. Perhaps that effect is real, > but we need to see a model to show how it comes to be. > > > > I might be able to help you write analytic signal code. > > > > Good wishes > > Gary Nelson > > > > > > Sent from my Windows 10 phone > > > > *From: *Claus Futtrup <cfutt...@gmail.com> > *Sent: *Saturday, May 26, 2018 7:41 AM > *To: *International users mailing list for Scilab. > <users@lists.scilab.org> > *Subject: *Re: [Scilab-users] Simulating phase modulation > > > > Hi Rafael > > > > Thank you, I shall print and study. :-) > > > > Cheers, > > Claus > > > > On Fri, May 25, 2018 at 8:42 PM Rafael Guerra <jrafaelbgue...@hotmail.com> > wrote: > > Hi Claus, > > > > I am not aware of such function. However, you can find simple code here > below for both phase modulation and demodulation, which is straightforward > to translate in Scilab: > > > https://www.gaussianwaves.com/2017/06/phase-demodulation-using-hilbert-transform-application-of-analytic-signal/ > > > > Note that the phase modulation is coded differently from you snippet below. > > > > Regards, > > Rafael > > > > *From:* users [mailto:users-boun...@lists.scilab.org] *On Behalf Of *Claus > Futtrup > *Sent:* Friday, May 25, 2018 7:17 PM > *To:* International users mailing list for Scilab. <users@lists.scilab.org > > > *Subject:* [Scilab-users] Simulating phase modulation > > > > Hi there > > > > In a loudspeaker the driver can move several millimeter in an attempt to > reproduce a low-frequency note. If the speaker also at the same time > produce a higher tone, this second tone is phase modulated by the first > one. This is a distortion of the original signal which I'd like to simulate > / illustrate with some simple Scilab code, if possible. > > > > In Matlab this can be simulated with pmmod. > > https://matlabandsimulink.wordpress.com/2013/03/12/phase-modulation/ > > > > Is there a similar function in Scilab? (name - please ?) > > > > Here's the code I have written so far - this is the part that shows the > input signal (the un-distorted signal): > > > > sample_rate=2; > > t = 0:1/sample_rate:0.6; > > N=size(t,'*'); *//number of samples* > > y1 = sin(2*%pi*50*t); > > y2 = 0.5*sin(2*%pi*500*t); > > *// y2 = 0.5*sin(2*%pi*500*t+%pi/4);* > > s=y1+y2+grand(1,N,'nor',0,1); > > > > *// Plot time-domain* > > endplot = round(N/15); > > twoplots = scf(); *// Set Current Figure (Graphics Window)* > > subplot(211); > > plot(t(1:endplot),y1(1:endplot),t(1:endplot),y2(1:endplot)); > > subplot(212); > > plot(t(1:endplot),y1(1:endplot)+y2(1:endplot)); > > > > y=fft(s); > > ymax = max(abs(y)); > > y = y ./ ymax; *// Normalize* > > > > *// s is real so the fft response is conjugate symmetric* > > *// and we retain only the first N/2 points* > > f=sample_rate*(0:(N/2))/N; *//associated frequency vector* > > n=size(f,'*'); > > fftplots = scf(); > > plot(f(2:$),abs(y(2:n))); *// drop first datapoint, f = 0 (it prevents > log-plot)* > > a = gca(); > > a.log_flags = "lnn"; > > > > Best regards, > > Claus > > ___ > users mailing list > users@lists.scilab.org > http://lists.scilab.org/mailman/listinfo/users > > > ___ > users mailing list > users@lists.scilab.org > http://lists.scilab.org/mailman/listinfo/users > ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
Re: [Scilab-users] Simulating phase modulation
Claus, Back in the late 60s, I did my PhD research using analytic signal. Yes,it works, and the implementation details are more complex that we find on the link. A few years ago, I implemented a system for analyzing harbor porpoise vocalizations using scilab. For example, instantaneous phase(t) wants to be differentiable if instantaneous frequency is to be positive. I found that octave bands are the widest that preserves this feature. Yes, you can calculate phase(t) = atan(imaginary/real), but you have to add 2PI when atan wraps around in order to make phase monotonically increase. Also, I am not convinced that a loudspeaker does phase modulation. Certainly, if the speaker is linear, then superposition applies. If phase modulation occurs, it is a non-linear effect. Perhaps that effect is real, but we need to see a model to show how it comes to be. I might be able to help you write analytic signal code. Good wishes Gary Nelson Sent from my Windows 10 phone From: Claus Futtrup Sent: Saturday, May 26, 2018 7:41 AM To: International users mailing list for Scilab. Subject: Re: [Scilab-users] Simulating phase modulation Hi Rafael Thank you, I shall print and study. :-) Cheers, Claus On Fri, May 25, 2018 at 8:42 PM Rafael Guerra <jrafaelbgue...@hotmail.com> wrote: Hi Claus, I am not aware of such function. However, you can find simple code here below for both phase modulation and demodulation, which is straightforward to translate in Scilab: https://www.gaussianwaves.com/2017/06/phase-demodulation-using-hilbert-transform-application-of-analytic-signal/ Note that the phase modulation is coded differently from you snippet below. Regards, Rafael From: users [mailto:users-boun...@lists.scilab.org] On Behalf Of Claus Futtrup Sent: Friday, May 25, 2018 7:17 PM To: International users mailing list for Scilab. <users@lists.scilab.org> Subject: [Scilab-users] Simulating phase modulation Hi there In a loudspeaker the driver can move several millimeter in an attempt to reproduce a low-frequency note. If the speaker also at the same time produce a higher tone, this second tone is phase modulated by the first one. This is a distortion of the original signal which I'd like to simulate / illustrate with some simple Scilab code, if possible. In Matlab this can be simulated with pmmod. https://matlabandsimulink.wordpress.com/2013/03/12/phase-modulation/ Is there a similar function in Scilab? (name - please ?) Here's the code I have written so far - this is the part that shows the input signal (the un-distorted signal): sample_rate=2; t = 0:1/sample_rate:0.6; N=size(t,'*'); //number of samples y1 = sin(2*%pi*50*t); y2 = 0.5*sin(2*%pi*500*t); // y2 = 0.5*sin(2*%pi*500*t+%pi/4); s=y1+y2+grand(1,N,'nor',0,1); // Plot time-domain endplot = round(N/15); twoplots = scf(); // Set Current Figure (Graphics Window) subplot(211); plot(t(1:endplot),y1(1:endplot),t(1:endplot),y2(1:endplot)); subplot(212); plot(t(1:endplot),y1(1:endplot)+y2(1:endplot)); y=fft(s); ymax = max(abs(y)); y = y ./ ymax; // Normalize // s is real so the fft response is conjugate symmetric // and we retain only the first N/2 points f=sample_rate*(0:(N/2))/N; //associated frequency vector n=size(f,'*'); fftplots = scf(); plot(f(2:$),abs(y(2:n))); // drop first datapoint, f = 0 (it prevents log-plot) a = gca(); a.log_flags = "lnn"; Best regards, Claus ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
Re: [Scilab-users] Simulating phase modulation
Hi Rafael Thank you, I shall print and study. :-) Cheers, Claus On Fri, May 25, 2018 at 8:42 PM Rafael Guerra <jrafaelbgue...@hotmail.com> wrote: > Hi Claus, > > > > I am not aware of such function. However, you can find simple code here > below for both phase modulation and demodulation, which is straightforward > to translate in Scilab: > > > https://www.gaussianwaves.com/2017/06/phase-demodulation-using-hilbert-transform-application-of-analytic-signal/ > > > > Note that the phase modulation is coded differently from you snippet below. > > > > Regards, > > Rafael > > > > *From:* users [mailto:users-boun...@lists.scilab.org] *On Behalf Of *Claus > Futtrup > *Sent:* Friday, May 25, 2018 7:17 PM > *To:* International users mailing list for Scilab. <users@lists.scilab.org > > > *Subject:* [Scilab-users] Simulating phase modulation > > > > Hi there > > > > In a loudspeaker the driver can move several millimeter in an attempt to > reproduce a low-frequency note. If the speaker also at the same time > produce a higher tone, this second tone is phase modulated by the first > one. This is a distortion of the original signal which I'd like to simulate > / illustrate with some simple Scilab code, if possible. > > > > In Matlab this can be simulated with pmmod. > > https://matlabandsimulink.wordpress.com/2013/03/12/phase-modulation/ > > > > Is there a similar function in Scilab? (name - please ?) > > > > Here's the code I have written so far - this is the part that shows the > input signal (the un-distorted signal): > > > > sample_rate=2; > > t = 0:1/sample_rate:0.6; > > N=size(t,'*'); *//number of samples* > > y1 = sin(2*%pi*50*t); > > y2 = 0.5*sin(2*%pi*500*t); > > *// y2 = 0.5*sin(2*%pi*500*t+%pi/4);* > > s=y1+y2+grand(1,N,'nor',0,1); > > > > *// Plot time-domain* > > endplot = round(N/15); > > twoplots = scf(); *// Set Current Figure (Graphics Window)* > > subplot(211); > > plot(t(1:endplot),y1(1:endplot),t(1:endplot),y2(1:endplot)); > > subplot(212); > > plot(t(1:endplot),y1(1:endplot)+y2(1:endplot)); > > > > y=fft(s); > > ymax = max(abs(y)); > > y = y ./ ymax; *// Normalize* > > > > *// s is real so the fft response is conjugate symmetric* > > *// and we retain only the first N/2 points* > > f=sample_rate*(0:(N/2))/N; *//associated frequency vector* > > n=size(f,'*'); > > fftplots = scf(); > > plot(f(2:$),abs(y(2:n))); *// drop first datapoint, f = 0 (it prevents > log-plot)* > > a = gca(); > > a.log_flags = "lnn"; > > > > Best regards, > > Claus > ___ > users mailing list > users@lists.scilab.org > http://lists.scilab.org/mailman/listinfo/users > ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
Re: [Scilab-users] Simulating phase modulation
Hi Claus, I am not aware of such function. However, you can find simple code here below for both phase modulation and demodulation, which is straightforward to translate in Scilab: https://www.gaussianwaves.com/2017/06/phase-demodulation-using-hilbert-transform-application-of-analytic-signal/ Note that the phase modulation is coded differently from you snippet below. Regards, Rafael From: users [mailto:users-boun...@lists.scilab.org] On Behalf Of Claus Futtrup Sent: Friday, May 25, 2018 7:17 PM To: International users mailing list for Scilab. <users@lists.scilab.org> Subject: [Scilab-users] Simulating phase modulation Hi there In a loudspeaker the driver can move several millimeter in an attempt to reproduce a low-frequency note. If the speaker also at the same time produce a higher tone, this second tone is phase modulated by the first one. This is a distortion of the original signal which I'd like to simulate / illustrate with some simple Scilab code, if possible. In Matlab this can be simulated with pmmod. https://matlabandsimulink.wordpress.com/2013/03/12/phase-modulation/ Is there a similar function in Scilab? (name - please ?) Here's the code I have written so far - this is the part that shows the input signal (the un-distorted signal): sample_rate=2; t = 0:1/sample_rate:0.6; N=size(t,'*'); //number of samples y1 = sin(2*%pi*50*t); y2 = 0.5*sin(2*%pi*500*t); // y2 = 0.5*sin(2*%pi*500*t+%pi/4); s=y1+y2+grand(1,N,'nor',0,1); // Plot time-domain endplot = round(N/15); twoplots = scf(); // Set Current Figure (Graphics Window) subplot(211); plot(t(1:endplot),y1(1:endplot),t(1:endplot),y2(1:endplot)); subplot(212); plot(t(1:endplot),y1(1:endplot)+y2(1:endplot)); y=fft(s); ymax = max(abs(y)); y = y ./ ymax; // Normalize // s is real so the fft response is conjugate symmetric // and we retain only the first N/2 points f=sample_rate*(0:(N/2))/N; //associated frequency vector n=size(f,'*'); fftplots = scf(); plot(f(2:$),abs(y(2:n))); // drop first datapoint, f = 0 (it prevents log-plot) a = gca(); a.log_flags = "lnn"; Best regards, Claus ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
[Scilab-users] Simulating phase modulation
Hi there In a loudspeaker the driver can move several millimeter in an attempt to reproduce a low-frequency note. If the speaker also at the same time produce a higher tone, this second tone is phase modulated by the first one. This is a distortion of the original signal which I'd like to simulate / illustrate with some simple Scilab code, if possible. In Matlab this can be simulated with pmmod. https://matlabandsimulink.wordpress.com/2013/03/12/phase-modulation/ Is there a similar function in Scilab? (name - please ?) Here's the code I have written so far - this is the part that shows the input signal (the un-distorted signal): sample_rate=2;t = 0:1/sample_rate:0.6;N=size(t,'*'); //number of samplesy1 = sin(2*%pi*50*t);y2 = 0.5*sin(2*%pi*500*t);// y2 = 0.5*sin(2*%pi*500*t+%pi/4);s=y1+y2+grand(1,N,'nor',0,1); // Plot time-domainendplot = round(N/15);twoplots = scf(); // Set Current Figure (Graphics Window)subplot(211);plot(t(1:endplot),y1(1:endplot),t(1:endplot),y2(1:endplot));subplot(212);plot(t(1:endplot),y1(1:endplot)+y2(1:endplot)); y=fft(s);ymax = max(abs(y));y = y ./ ymax; // Normalize // s is real so the fft response is conjugate symmetric// and we retain only the first N/2 pointsf=sample_rate*(0:(N/2))/N; //associated frequency vectorn=size(f,'*');fftplots = scf();plot(f(2:$),abs(y(2:n))); // drop first datapoint, f = 0 (it prevents log-plot)a = gca();a.log_flags = "lnn"; Best regards, Claus ___ users mailing list users@lists.scilab.org http://lists.scilab.org/mailman/listinfo/users
